(1) Field of the Invention:
The present invention relates to a divisionally time-compressed subsampling transmission and motion compensated reproduction system for a wide-band high definition color television picture signal. The system sends narrow band transmission conditioned at a sending end and restores the original form at a receiving end under the most suitable processing adapted to the conditioning, particularly the most suitable interpolation adapted to the subsampling at the sending end, so as to maintain high definition at the receiving end.
(2) Description of the Prior Art:
The standard of the high definition color television picture signal of this kind has not yet been unified into an international one, but the following standards are in the course of investigation.
Number of scanning lines: 1,125 PA0 Aspect ratio: 5:3 PA0 Interlace ratio: 2:1 PA0 Field frequency: 60 Hz PA0 Video signal frequency band: PA0 Luminance signal bandwidth: 20 MHz PA0 Wide-band chrominance signal bandwidth: 7.0 MHz PA0 Narrow-band chrominance signal bandwidth: 5.5 MHz
As is apparent from the above, even only with respect to the luminance signal bandwidth, a high definition television system requires an extremely wide-band transmission signal, about five times that of the present standard television system. Fruther, the signal is accompanied with two kinds of chrominance signals. Therefore, plural narrow transmission channels are required for the transmission of single channel of the high definition television system.
As an example of a transmission channel which is not perfectly suitable but substantially adapted to the transmission of the high definition television system, particularly to the broadcast thereof, a satellite broadcast channel is worthy of note. In this connection, the bandwidth per channel in the 12 GHz band, which is alloted to the third zone including Japan for broadcast business use, is 27 MHz as decided in 1979 at the World Administration Radio Conference on Broadcast Satellite.
The satellite channel is best suited for transmission by frequency modulation systems capable of obtaining a wide band and high gain. This is because it is an analog transmission channel and is restricted in sending power. For instance, the above-mentioned bandwidth per channel of 27 MHz allotted for broadcast business can transmit a signal having a base band of only one third thereof. Accordingly, a high definition television picture signal can be transmitted at one time by employing four or five channels of the broadcast satellite transmission. However, realization thereof is regarded as extremely difficult due to the inefficient utilization of the transmission channel.
To efficiently use the transmission channel, it is most desirable that the high definition color television picture signal be transmitted through a signal channel of the broadcast satellite transmission. Therefore, unification of the high definition color television picture signal consisting of luminance signal components and chrominance signal components and drastically compressing the extremely wide frequency band thereof is required.
The above required unification and band compression will be described hereinafter.
As mentioned above, the broadcast satellite transmission is best adapted to a frequency modulation system. However, frequency modulation transmission is accompanied with so-called triangular noise, the power of which increases proportional to the frequency. Therefore, for transmission of a wide band signal unified by frequency multiplexing, such as the color television signal of the NTSC system of the HLO-PAL system, frequency modulation is unfavorable because of noise and crosstalk.
On the other hand, the time compressed integration system, that is, the co-called TCI system, for example the MAC system of the European Broadcast Union, is regarded as suited to frequency modulation transmission. In this TCI system, wide-band and narrow-band chrominance signals C.sub.W and C.sub.N, time axes of which are respectively compressed, are multiplexed with a luminance signal Y, for instance, by being inserted into a line retracing period thereof, so as to obtain a unified color television picture signal.
As is apparent from the above, in the NSC system or the HLO-PAL system, a composite color television picture signal is obtained by frequency-multiplexing the chrominance signals with the luminance signal, while, in the TCI system, a kind of analog component color television picture can be obtained. Thus, the unified color television picture signal of this TCI system is free from the problems of crosstalk between the chrominance signals and the luminance signal, and the differential gain or the differential phase of the NTSC system is not affected by the nonlinear performance of the transmission channel. Consequently, the TCI system can be regarded as adaptible to transmission of frequency modulation. In this regard the bandwidth of the TCI signal is widened after compression of time axes thereof in spite of the unification.
Regarding frequency band compression of satellite transmission of high definition color television picture signals, among various systems worthy of investigation, the so-called subsampling system can be adapted for a band compression system capable of drastic compression, for instance, into one twentieth. This subsampling system can be regarded as a two-dimensional dot-interlace scanning system in which a specified element in a television picture is scanned once, for instance, every four field periods. Thus, a stationary television picture signal can be completely transmitted every four field periods with a compressed bandwidth of one fourth of the original bandwidth. The subsampling system seems to be promising for drastic compression of the bandwidth.
However, this subsampling system has the following problems. In the subsampling system, as mentioned above, a specified element in a television picture is scanned once every four field periods, so that a high degree of interpolation of skipped picture elements is required for the restoration of the original television picture every field period.
First, with regard to a motion picture region and a quasi-stationary picture region resulting from the panning of a television camera, interpolation of picture elements must be adapted for each picture.
Second, even with a stationary picture region, interpolation of skipped picture elements is required at exact timings of each of every four field periods.